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Surgical Technique of Corneal Transplantation in Rabbits⋆
FREDERICK C. STANSBURY AND JOSEPH A. C. WADSWORTH 968 "Groenblad, E. Angioid streaks. Arch, of Ophth., 1939, v. 21, p. 746. 'Hallopeau and Lafifite. Nouvelle note sur un cas de Pseudoxanthome elastique. Annales de Derm, et Syphil., 1903, v. 4, p. 595. ' Nomland, R., and Klien, B. Pseudoxanthoma elasticum of skin. Arch, of Derm. & Syph., 1933, 27, p. 894. ° Finnerud, C. W. and Nomland, R. Pseudoxanthoma elasticum, proof of calcification of elastic tissue. Arch. Dermat. & Syph., 1937, v. 35, 653. Terry, T. L. .Angioid streaks and osteitis deformans. Trans. Amer. Ophth. Soc, 1934, v. 32, p. 555. " Lambert, R. K. Paget's disease with angioid streaks of retina. Arch, of Ophth., 1939, v. 22, p. 106. "Morrison, W. H. Osteitis deformans with angioid streaks. Arch, of Ophth., 1941, v. 26, p. 79. "Wells, H. G., and Holley, S. W. Metastatic calcification in osteitis deformans. Arch, of Path., 1942, V. 34, p. 435. " Seligman, B., and Nathanson, L. Metastatic calcification in soft tissues of legs in osteitis de formans. An. Int. Med., 1945, v. 23, p. 82. V.
SURGIC.XL T E C H N I Q U E O F IN
CORNEAL TRANSPLANTATION RABBITS*
A D i s c u s s r o N OF T H E PROBLEMS ENCOUNTERED AND SUGGESTIONS FOR T H E I R SOLUTION FREDERICK C . STANSBURY, M . D . , AND J O S E P H A . C . W A D S W O R T H , M . D .
New
The difficulty with which corneal trans plantation is successfully accomplished is such that it is seldom attempted on human subjects until the surgeon has acquired some skill with the procedure on experi mental animals. T h e laboratory animal best adapted to this operation, from the point of view of both expense and avail ability, is the rabbit. All of the pioneers in this new field of ophthalmic surgery (Castroviejo, 1931, etc.; Filatov, 1935, etc.; Thomas, 1930, etc.) have experi mented at length on rabbits before pro ceeding to human patients. These men have written about the different types of operation practised by them individually on human beings, but no one has given a detailed account of the surgical technique employed in keratoplasty on the rabbit. The purpose of this paper is, therefore, to describe in detail the procedure ofkeratoplasty on rabbits, and the difficul-
York
ties encountered in this operation, follow ing in general the technique employed by Castroviejo. T E C H N I Q U E OF T R A N S P L A N T A T I O N PROBLEMS ENCOUNTERED
There are problems in transplantation of the rabbit's cornea that are not en countered in the same operation on the human cornea. T h e rabbit's cornea is thinner than that of man, and this fact makes the placing of the suture, the appo sition of the cut surfaces, and the pre vention of postoperative bulging more difficult. Anesthesia is a trying procedure and some animals may die on the operat ing table. It is not feasible to bandage the rabbit's eye, and one must resort to lid sutures—an unsatisfactory method, to say the least, when a pressure bandage is desired. Infection is difficult to prevent in any laboratory animal, and the rabbit is no exception. T h e postoperative bed rest and immobility, which are prescribed
* From the Institute of Ophthalmology of the Presbyterian Hospital, New York City.
CORNEAL T R A N S P L A N T A T I O N
for the human patient after keratoplasty, are quite obviously out of the question for the rabbit. Once the surgeon is able to overcome these operative difificulties peculiar to the rabbit and is able to per fect his surgical procedure on this ani mal, he is better prepared to operate upon the human being. T h i s paper will discuss the operation of square, partial penetrating keratoplasty, and will give an account of the equip ment needed, the preparation of the rab bit, the surgical procedure, as well as the management of the difficulties encoun tered. EQUIPMENT REQUIRED FOR THE
OPERA
TION
IN RABBITS
969
for last-minute manipulations of the graft when tightening and tying the suture. ( 5 ) Fine needle holder, for placing the sutures and tying. ( 6 ) Elschnig's fixa tion forceps, for grasping the episclera and fixing the eye. ( 7 ) Fixation forceps, for holding the lids when they are sutured together. ( 8 ) Scissors, for cut ting the sutures. ( 9 ) Mosquito clamp, for holding the moss suture in the center of the window being cut out of the recipi ent's cornea. (10) Small, straight, tooth less forceps for tightening suture. (11) Small, curved, toothless forceps, for tight ening the suture. (Oftentimes either the straight or curved forceps will also be used for tying the suture.) (12) Specu lum, for separation of the lids. ( 1 3 ) 7-0 double-armed black silk suture with atrau matic needles.
A narrow operating table, not over 12 inches in width and about 4 feet long, will be found very practicable for rabbit surgery. T h e height can be varied accord ing to the standing or sitting position of the operator. T h e narrow table is desir able in order that both operator and assis tant may be able easily and comfortably to reach the operative field. Any one of the common small instrument tables is satisfactory for the instruments. A good operating lamp of the hammer type pro vides satisfactory illumination. Other needed items—scrub sink, sterilizer, and so forth—will be found in any wellequipped animal operating room.
T h e following solutions and ointments are recommended: ( 1 ) 3-percent atropinesulfate solution. ( 2 ) Sodium-pentobarbital solution (45 mgm. per cc. of 10-per cent alcohol solution). ( 3 ) 4-percent co caine solution. ( 4 ) 20-percent argyrol solution. ( 5 ) Sterile physiologic saline solution. ( 6 ) 2-percent fluorescein solu tion. ( 7 ) 1-percent sodium citrate solu tion. ( 8 ) Adrenalin solution (1:1,000). ( 9 ) Penicillin ophthalmic ointment. ( 1 0 ) 1-percent atropine-sulfate ointment.
T h e following instruments (fig. 1) are necessary: ( 1 ) Castroviejo double-bladed knife, for marking the limits of the win dow in the recipient's eye and the limits of the graft in the donor eye. ( 2 ) Castroviejo's special keratome, 4-mm. wide, for making the initial incision into the an terior chamber in both the recipient and the donor eyes. ( 3 ) Modified de Wecker scissors, for cutting the remainder of the incision in both eyes. ( 4 ) Spatula, for lifting the graft from the donor eye and placing it in the recipient eye, and also
I n selecting rabbits for keratoplasty, it is well to obtain an animal weighing five pounds or more. Smaljer rabbits may be used, but the operation becomes more dif ficult on the smaller eye. T h e rabbits should be obtained sufficiently far in ad vance of the operation so that they may occupy their new quarters for at least 10 days prior to surgery. A small percentage of rabbits will die when removed to the small cages that constitute their quarters in the medical school or hospital. Further, it has been found that new rabbits do not
PREPARATION OF THE RABBIT
970
• R E D E R I C K C. S T A N S B U R Y A N D J O S E P H Α. C. W A D S W O R T H
Fig. 1. (Slarisbury and Wad.sworth). Recommended instruments: (1) Castroviejo doublebladed corneal knife; (2) Castroviejo special keratome; (3) modified de Wecker scissors; (4) spatula; (5) needle holder; (6) Elschnig's fixation forceps; (7) fixation forceps; (8) scissors; (9) clamp; small straight toothless forceps; small, curved, toothless for ceps ; (12) speculum.
mosquito
(10)
do well postoperatively. On the other hand, rabbits that are well acclimated to their lot will usually take the anesthesia and operation uneventfully. Six hours prior to the operation, the rabbit is brought to the animal operating rooms, and atropinization of the desig nated eye is started. A drop of 3-percent atropine-sulfate solution is instilled into this eye each hour for six doses. Sodium pentobarbital, intravenously, is used for the anesthesia. A solution is made of 45 mgm. of sodiurn pentobarbi
(11)
tal per cc. of 10-percent alcohol solution, and 1 cc. of the resulting solution is given for each kilogram of body weight. Three fourths of the estimated dosage is slowly injected intravenously lyi hours before operation, and the remainder of the cal culated amount is given one-half hour be fore operation. This will usually be suf ficient, but sometimes it is necessary to introduce a very small additional amount just before fastening the animal into the clamp. After the second injection of sodium
CORNEAL TRANSPLANTATION IN RABBITS pentobarbital, the rabbit will lie quiet and submit to the trimming of the hair around the operative field. T h e hair is re moved from an area at least one centi meter wide around the eye. In addition, all the long whiskers on that side of his head are cut. At this time, a drop of 4percent cocaine solution is instilled into the conjunctival sac. The rabbit is then placed on the operat ing table and fastened into the special clamp (fig. 2 ) . The head is adjusted to fit snugly into the clamp, and the screw is turned down. T h e animal is further immobilized by lashing the extremities to the table (fig. 3 ) . Twenty-percent argyrol solution is then instilled into the conjunc tival sac, washed out with sterile saline, and another drop of 4-percent cocaine solution is instilled. A small sterile sheet, with a diamond-shaped opening for the
Fig. 2 (Stansbury and Wadsworth). Clamp for immobilization of the rabbit. eye, is then placed over the rabbit and fastened with two towel clamps. SURGICAL PROCEDURE
Separation of the lids is obtained by means of the standard eye speculum. Care must be taken when inserting the specu lum to be sure the nictitating meinbrane of the rabbit is caught behind one arm of the speculum. The eyeball is then fixated with Elschnig's forceps, and the area to be removed is marked out with the double-
971
bladed Castroviejo knife. T h e blades of this knife have previously been treated with 2-percent fluorescein solution, so that the knife cuts and stains the cornea
Fig. 3 (Stansbury and Wadsworth). Immobi lization clamp with the rabbit in position. at the same time. Using a 7-0 doublearmed silk corneal suture with atrau matic needles, the continuous corneal suture of Castroviejo is then inserted, placing all the bites 1 mm. from the fluorescein-stained incision (fig. 4 ) . It is our practice to begin the first bite at the 9-o'clock position and to come out at the lower left-hand corner of the s q u a r e ; to begin the second bite at the upper right-hand corner of the square and to come out at the 12-o'clock posi tion ; to begin the third bite at the 6o'clock position and to come out at the lower right-hand corner; to begin the fourth bite at the upper left-hand corner and to come out at the 9-o'clock position. T h e last bite begins at about the 3-o'clock position and comes out about 3 mm. from the limbus. As each bite is placed, the loop of suture so formed is placed be yond the upper left corner of the square. Each succeeding loop is placed on top of the preceding one. O n e end of the suture is then cut off, and a bite is placed in the middle of the square. T h e two ends of this last suture are then fastened in a mosquito clamp.
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FREDERICK C. S T A N S B U R Y A N D J O S E P H A. C. W A D S W O R T H
A keratome incision is then made in the lower right-hand corner of the square, beveling it in the manner described by Castroviejo and Thomas. Care must be exercised in this maneuver to avoid injur ing the lens. By making this incision in the corner of the square, only one cut is left on that leg of the square to be done with scissors. As soon as the anterior
ner. Finally, the upper end is finished in the same manner. While the assistant con tinuously drops citrate solution over the operative field, a similar graft is excised from the donor eye, using the same pro cedure, except that no Moss suture is used, and the instruments are not tilted when cutting. The graft is then picked up with the
Fig. 4 (Stansbury and Wads worth). Steps in placing the suture in the cornea, with arrangement of the loops. chamber is opened, the assistant begins instilling 1-percent sodium-citrate solu tion into the conjunctival sac (to avoid formation of fibrin). While the square is lifted a slight distance above the lens with the mosquito clamp attached to the Moss suture, the lower blade of the de Wecker scissors, tilted in the same manner as was the keratome, is then passed through the keratome incision and the remainder of the lower leg of the square is completed. The scissors are turned and the left hand side of the square is cut. T h e scissors are then brought down to the lower righthand corner of the window, and the righthand side is completed in the same man-
spatula and gently placed in the window in the recipient's cornea. Any rolling of the edges or corners is corrected with the spatula. Then the suture is tightened, us ing the small straight and the small curved utility forceps. W e begin to tighten with the last suture inserted and work backwards to the first one (fig. 5 ) . W h e n all the sutures are snug, and the graft is in good position, a surgeon's knot is tied at the 3-o'clock position, near the limbus. T h e instillation of the citrate solution is then stopped, and a drop of 3-percent atropine solution is instilled. At this point, we inject a small amount of adrenalin solution (1:1,000) subconjunc-
CORNEAL TRANSPLANTATION IN RABBITS tivally. Three through-and-through lid sutures are then put in position—one in the center of the lids, and one 3 to 4 mm. to each side. Before the last suture is tied, penicillin ophthalmic ointment is injected into the conjunctival sac. W h e n the rabbit is taken back to his quarters, a meshed-wire floor is placed in his cage instead of straw. Every other day, postoperatively, 1-percent atropine
973
DISCUSSION ANESTHESIA
Probably no one factor has given us more concern than the administration of the anesthesia. T h e first system tried was to calculate the amount of pentobarbital to be given and to make a slow intra venous injection of this amount. Many rabbits will go into respiratory failure
Fig. 5 (Stansbury and Wadsworth). Final steps in completion of the suture. ointment and penicillin ophthalmic oint ment are instilled into the conjunctival sac. One week after operation, the ani mal is again given the sodium-pentobarbital anesthesia, and the sutures are re moved. If anterior synechiae are present, they are broken up with adrenalin subconjunctivally, or neosynephrin or atro pine in the conjunctival sac. If infection is present, penicillin is used as long as necessary. It is desirable to keep the rab bit 6 to 8 months postoperatively to de termine whether or not the graft will re main transparent.
within 15 minutes if this is done. Once administered, there is practically nothing the operator can do to lighten the effects of the anesthetic. Nonvolatility is one of the characteristics of the barbiturates that makes for a prolonged and continuous anesthesia. This same nonvolatility pre cludes their excretion through the lungs, and so the concentration depends solely on the dosage. Once too much is given, we have been unable to resuscitate the rab bit. Since this was the case, we tried to weigh the rabbit more carefully and to calculate the dosage more accurately. The
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FREDERICK C. STANSBURY AND fOSEPH A. C. WADSWORTH
response to pentobarbital is quite variable in dif¥ercnt rabbits, however, as it is in human beings. Large rabbits may die with less than the calculated dosage, and small ones may require double the estimated amount. T h e attempt was made to give the anes thetic intraperitoneally, but here the ab sorption was very slow and irregular. Large amounts are required for deep anesthesia, and the large number of doses and the amount of lime required to watch the animals precluded this method. A weaker solution of sodium pentobarbital was tried, but this was not found to be satisfactory. Finally, fractionalization of the anes thesia was worked out, and this system has proved satisfactory. Three fourths of the estimated dosage is slowly given in an ear vein 1 ^ hours before operation. One hour later, if the rabbit is not too slug gish, the rest of the dose is given. Just before fastening the animal in the clamp, additional pentobarbital is given as needed. This method of fractionalization of the administration of the anesthesia has resulted in no deaths. S K I ' A R A T I O N OK T H E
t.lDS
Wide separation of the eyelids, without the interference of cumbersome instru ments, is necessary during the operation: (1) lo provide an operative field, and ( 2 ) to prevent pressure on the globe. In the rabbit we have tried three methods of holding the lids a p a r t : ( 1 ) the conven tional speculum, (2) sutures through the lids, and ( 3 ) Castroviejo mosquito lidclamps. Advantages of the speculuin are ease and quickness of insertion and eliinination of trautna to the lids. Some workers (Castroviejo, 1941,) believe that it inter feres to some slight degree with instru mentation in the operative area, especially during use of the double-bladed knife,
and that it does not provide as large an exposure as the other two methods. Lid sutures provide a satisfactory op erative field and arc particularly effica cious in immobilizing the nictitating mem brane. However, their disadvantages are considerable. They are painful and often arouse the rabbit. They may cause hema tomas of the lids. They often result in bleeding, and blood in the conjuncti\-aI sac, postoperatively, is undesirable be cause it forms an excellent medium for bacterial growth. Castroviejo's lid clamps also provide a good field and do not have the disadvan tages of the lid sutures. Nevertheless, the small drape used in rabbit surgery does not constitute a good anchor. Lid sutures and lid clamp may produce loo much trac tion and may cause tenting of the lids, which will result in poor exposure. .^fter trying the second and third meth ods on a number of rabbits, the first method—the use of the lid speculum— was adopted as the least traumatic and the most facile procedure. It is comparaliveh' easy to avoid touching the speculum with any of the cutting instruments simply by rotating the globe with the fixation for ceps until the cornea is in the desired posi tion. Katzin (1946) advocated complete immobilization of the globe by radial su tures in the limbus. This type of immobili zation, in our opinion, is un.satisfactory, not only because its use may endanger the eye but also because it may compel the surgeon to work from awkward angles. M A R K I N G T H E CORNEA
Correct marking of the cornea can be a great help in facilitating a successful transplant. If it is incorrectly done, how ever, the remainder of the procedure may be hindered by numerous unnecessary difficulties. T h e blades of the Castroviejo knife must be parallel and set firmly at the desired width (5 mm. for rabbits).
CORNEAL TRANSPLANTATION IN RABBITS If the blades are not parallel, the result ing wide, ragged line will make it difficult to maintain a perfect square when the window is removed with the scissors. T h e knife must be gently placed on the cornea in such a manner as to exert equal pressure on both blades; otherwise un even lines will be made. Pressure should be sufficient to penetrate the epithelium only. If the marking is too deep, the lines tend to gape and the staining becomes diffuse. Care must be taken not to carry the lines too far along the cornea and cause unnecessary damage to the recipi ent epithelium. T h e second marking must be perpendicular to the first, or a square window will not result. It has been our experience, as well as that of other workers (Carpenter and Smyth, 1946), that fluorescein on a rab bit's cornea will stain the entire cornea in a short time. However, we found that, by applying fluorescein to the knife and al lowing it to dry before marking the cor nea, the treated knife made very fine lines, which had less tendency to dififuse. In marking the donor eye, it is advis able to hold the eye gently in order not to stretch the globe; otherwise, the trans plant may be too small for the prepared area. In addition, if the eye is held too firmly, the lens will be pushed forward and its capsule will be ruptured while the transplant is being removed. Although this is not any great mishap, it adds to the difficulty of accurately cutting and re moving the prepared square. PLACING THE SUTURE
It is essential to the success of a kera toplasty that the suture holding the graft in place be located with exact pre cision. T h e suture in the corneal stroma should be approximately 1 mm. from the incision. If it is placed closer than 1 mm., it is difficult to cut the window without severing the suture. If it is placed farther
975
than 1 mm., it will tend to buckle the ap proximated edges of the cornea and the graft when the suture is tightened at the end of the operation. Furthermore, it is very important that the suture be placed so that the arms of the suture, as they crisscross over the graft, cross exactly over each comer, because these are fa vorite locations for bulging. T h a t means that the suture must enter the cornea pre cisely opposite the apex of the right angle that forms each corner of the window. It was for this reason that Thomas gave up square transplants in favor of the circu lar form (Thomas, 1930). T h e cornea puts up considerable re sistance to the passage of the needle through its substantia propria. If the op erator pulls away from the fixation for ceps, the conjunctiva will not withstand the traction exerted in placing the suture but will give way at the limbus. H o w ever, if the fixation forceps are applied in such a manner that the force of the needle pushes toward the forceps, this ac cident will not occur. W h a t to do with the loops of suture while the operation is being finished is another one of the problems encountered. In order to avoid a snarl of the loops at the time when one wants to tie quickly ^ n d close the wound, it was found neces sary to place the loops to one side in a definite pattern. W e now lay all the loops of the suture to the upper left side, in the following manner. T h e first loop, which may be called the 7-to-l loop, using the numbers as they appear on the face of the clock, is placed to the upper left, over the free end of the suture coming out at the 9-o'clock position. The second loop, called the 12-to-6 loop, is placed above the 7-to-l loop. Likewise the third loop, the 5-to-ll loop, is placed above the 12-to-6 loop, and finally the 9-to-3 loop is placed above the other three. T h e free end extends off to the right (fig. 4 ) .
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FREDERICK C. STANSBURY AND JOSEPH A. C. WADSWORTH
Some operators place the entire suture, tighten the loops ready to tie, and then loosen the loops again, presumably to be sure the loops are located properly. This has been found unnecessary, provided the systematic steps outlined above are fol lowed. W h a t should be done if a leg of the suture is cut during the operation? W e have found that the corneal canals are very easy to relocate and that the needles will pass through the canals without fric tion; so the cut suture is pulled out and a new one inserted. If one goes too deep with the needle and perforates into the anterior chamber, the needle should be removed and a new canal made. This step is necessary to avoid formation of a fis tula. PROBLEM OF FIBRIN
T h e presence of fibrinogen in the nor mal aqueous of the rabbit results in the formation of fibrin as soon as the an terior chamber is opened, and may be a great bother in the completion of a kera toplasty. It has been our experience, as well as that of others (Thomas, 1934), that a solution of sodium citrate in nor mal saline will obviate the formation of fibrin. Just as soon as the anterior chamber is opened, a continuous drip of 1-percent sodium citrate in saline should begin and be continued until the suture has been tightened and tied. If such a system is not maintained, troublesome collections of fibrin will accumulate within the win dow of the cornea and will render the placement of the graft more difficult. The loops of the suture must also be bathed in the citrate, or the firm snarling of the loops will endanger proper placement and lessen the chances for a satisfactory transplant. Not infrequently the coagula tion may be so severe and firm that it is almost impossible to separate the sutures
from one another. T h e removal of the fibrin is so tedious and traumatic that the graft may be poorly placed. Soaking of the suture material in citrate before the sutures are placed in the cornea will help to maintain their pliability and softness. TYING THE SUTURE
T h e mere matter of tightening the loops and tying the suture would appear very simple, but such is not always the case. If the loops are not kept in some pattern so that the operator can identify them, he will find a snarl of silk before him. However, if they are arranged as has been described, the tying can be ex pedited. W e use the two small forceps, one for lifting up the loop and the other for pull ing it through the cornea. First we lift up the 9-to-3 loop and pull it through loosely (fig. 5 ) , pulling on the free end of the suture near the limbus at the 3-o'clock position. Next the 5-to-ll loop is lifted up and pulled through at the 6-o'clock position. Then we lift up the 12-to-6 loop and pull it through at the 1-o'clock posi tion. Finally, the 7-to-l loop is lifted up and pulled through at the 9-o'clock posi tion. T h e apposition of the graft is then checked all around the periphery, using the spatula for any necessary adjust ments. W i t h the same two forceps, this pro cedure is now repeated and all the loops are given a final tightening. T h e y are pulled as tight as can be done without dimpling or buckling the cornea at any place, either on the graft or on the recipi ent's own cornea. This is very important, because the suture controls the apposi tion of the cut surfaces and, if snug enough, prevents bulging. T h e suture is tied near the limbus, first with a surgeon's knot to hold the wet suture material and then with a conventional tie. Finally, the spatula may be inserted between the
CORNEAL TRANSPLANTATION IN RABBITS
977
Fig. 6. (Stansbury and Wadsworth). Pictures of rabbits after transplantation. (1), (2), and (3) show successful results. (4) is a postoperative ectasia. center of the graft and the crossing loops of the suture and gently lifted once or twice, to give a last general distribution of the tension of the suture. L I D CLOSURE
Simple through-and-through fine black silk sutures, placed at equal intervals through the lid margins, give a very sat isfactory closure of the lids. Numerous other methods were tried in an endeavor to obtain pressure, but various disadvan tages precluded their adoption. T w o mat tress sutures were tried, but they were more traumatic and several troublesome postoperative infections resulted. M o r e over, they frequently pulled through,
probably the result of the rabbit's efforts to remove the uncomfortable sutures. In an effort to maintain pressure, a wide overlapping of the lids with mattress su tures was tried, but the resulting irrita tion and secondary infection made this method impracticable. POSTOPERATIVE ECTASIA
O n e of the difficulties we have not been able to overcome is the postoperative bulg ing of the central portion of the cornea, including the graft. Often, when we re move the sutures on the 7th or 8th day, we find the graft in good position, the anterior chamber reformed, no synechiae and no infection, only to be followed a
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F R E D E R I C K C. S T A N S B U R Y A N D J O S E P H A. C. W A D S W O R T H
day or two later
by very considerable
sutures one week after operation and the
bulging of the whole center of the cornea,
corneal suture about 10 days postopera-
with the graft at the apex of the conus.
tively. W e have not employed this system
Some of these cases have progressed sat-
long enough to determine its efficacy.
isfactorily to complete healing of the scar,
CONCLUSION
and the graft has remained in place and transparent for over six months (fig. 6 ) . W e attribute this type of unsuccessful re_-
A satisfactory method of
keratoplasty
on rabbits, following in general the tech-
sult to our inability to apply a pressure
nique of Castroviejo, is described. A list
bandage to the rabbit's eye. These obser-
of the necessary equipment and a detailed
vations make fibrin fixation of the cornea
description of the procedure followed are
without suture (Katzin, 1946) appear a
recorded. T h e numerous
most unlikely procedure. W e h a v e been
countered, and our methods of
unable to prevent this condition in some
these difficulties are discussed,
rabbits, although we now remove the lid
635 West
165th Street
difficulties
en-
solving
(32).
REFERENCES Bellows, J. G. Influence of local antiseptics on regeneration of corneal epithelium in rabbits. Arch' of Ophth., 1946, v. 36, July, p. 70. Carpenter, C. P., and Smyth, H . F. Chemical burns of the rabbit cornea. Amer. Jour. Ophth., 1946, V. 29, Nov., p. 1363. Castroviejo, R. New Method of corneal transplantation: Final report. Proc. Staff. Meet. Mayo Clinic, 1931, v. 6, Nov. 11, p. 669. . Keratoplasty: An historical and experimental study, including a new method. Amer. Jour. Ophth., 1932, v. 15, Sept., p. 825; Oct., p. 905. . Present status of keratoplasty. Arch, of Ophth., 1939, v. 22, July, p. 114. . Mosquito lid-clamp retractors. Amer. Jour. Ophth., 1939, v. 22, p. 1018. Keratoplasty. Amer. Jour. Ophth., 1941, v. 24, Jan., p. 1; Feb., p. 139. Filatov, \". P. Transplantation of the cornea. Arch, of Ophth,, 1935, v. 13, Mar., p. 321. . Experimental transplantation of the dried and frozen corneas. Vestnik. oftal., 1940, V. 17, p. 536. Transplantation of the cornea, Amer, Rev, Sov, Med,, 1944, v. 2, D e c , ii. 159. Katzin, H. M. Aqueous fibrin fixation of corneal transplants in the rabbit. Arch, of Ophth., • 1946, v. 35, Apr., p. 415. . Animal operating equipment for experimental ocular surgery. Arch, of Ophth,, 1946, v. 36, Aug., p. 215. Sollmann, Τ. A Manual of Pharmacology and Its Api)lication to Therapeutics and Toxicology. Philadelphia, W, B, Saunders Co,, 1937. Thomas, W . T, Transplantation of the cornea: A preliminary report on a series of experi ments in rabbits, together with a demonstration of four rabbits with clear corneal grafts. Trans. Ophth. Soc, United Kingdom, 1930, v, 50, p. 127. . Successful grafting of the cornea in rabbits. Lancet, 1931, v. 1, Feb. 14, p. 335. . Return of sensitivity in grafts in rabbits. Proc. Roy. Soc. Lond., 1931, v. 108, June, l , p . 301. . Transplantation of scleral tissue on to a rabbit's cornea. Trans, Ophth, Soc. United Kingdom, 1932, v, 52, p. 64, . Experimental grafts of devitalized corneal tissue. Trans. Ophth. Soc. United King dom, 1934, V . 54, p. 119. Experimental heterogenous corneal grafts. Trans, Ophth, Soc, United Kingdom, 1936, V. 56, p. 97.
SURGIC.XL T E C H N I Q U E O F IN
CORNEAL TRANSPLANTATION RABBITS*
A D i s c u s s r o N OF T H E PROBLEMS ENCOUNTERED AND SUGGESTIONS FOR T H E I R SOLUTION FREDERICK C . STANSBURY, M . D . , AND J O S E P H A . C . W A D S W O R T H , M . D .
New
The difficulty with which corneal trans plantation is successfully accomplished is such that it is seldom attempted on human subjects until the surgeon has acquired some skill with the procedure on experi mental animals. T h e laboratory animal best adapted to this operation, from the point of view of both expense and avail ability, is the rabbit. All of the pioneers in this new field of ophthalmic surgery (Castroviejo, 1931, etc.; Filatov, 1935, etc.; Thomas, 1930, etc.) have experi mented at length on rabbits before pro ceeding to human patients. These men have written about the different types of operation practised by them individually on human beings, but no one has given a detailed account of the surgical technique employed in keratoplasty on the rabbit. The purpose of this paper is, therefore, to describe in detail the procedure ofkeratoplasty on rabbits, and the difficul-
York
ties encountered in this operation, follow ing in general the technique employed by Castroviejo. T E C H N I Q U E OF T R A N S P L A N T A T I O N PROBLEMS ENCOUNTERED
There are problems in transplantation of the rabbit's cornea that are not en countered in the same operation on the human cornea. T h e rabbit's cornea is thinner than that of man, and this fact makes the placing of the suture, the appo sition of the cut surfaces, and the pre vention of postoperative bulging more difficult. Anesthesia is a trying procedure and some animals may die on the operat ing table. It is not feasible to bandage the rabbit's eye, and one must resort to lid sutures—an unsatisfactory method, to say the least, when a pressure bandage is desired. Infection is difficult to prevent in any laboratory animal, and the rabbit is no exception. T h e postoperative bed rest and immobility, which are prescribed
* From the Institute of Ophthalmology of the Presbyterian Hospital, New York City.
CORNEAL T R A N S P L A N T A T I O N
for the human patient after keratoplasty, are quite obviously out of the question for the rabbit. Once the surgeon is able to overcome these operative difificulties peculiar to the rabbit and is able to per fect his surgical procedure on this ani mal, he is better prepared to operate upon the human being. T h i s paper will discuss the operation of square, partial penetrating keratoplasty, and will give an account of the equip ment needed, the preparation of the rab bit, the surgical procedure, as well as the management of the difficulties encoun tered. EQUIPMENT REQUIRED FOR THE
OPERA
TION
IN RABBITS
969
for last-minute manipulations of the graft when tightening and tying the suture. ( 5 ) Fine needle holder, for placing the sutures and tying. ( 6 ) Elschnig's fixa tion forceps, for grasping the episclera and fixing the eye. ( 7 ) Fixation forceps, for holding the lids when they are sutured together. ( 8 ) Scissors, for cut ting the sutures. ( 9 ) Mosquito clamp, for holding the moss suture in the center of the window being cut out of the recipi ent's cornea. (10) Small, straight, tooth less forceps for tightening suture. (11) Small, curved, toothless forceps, for tight ening the suture. (Oftentimes either the straight or curved forceps will also be used for tying the suture.) (12) Specu lum, for separation of the lids. ( 1 3 ) 7-0 double-armed black silk suture with atrau matic needles.
A narrow operating table, not over 12 inches in width and about 4 feet long, will be found very practicable for rabbit surgery. T h e height can be varied accord ing to the standing or sitting position of the operator. T h e narrow table is desir able in order that both operator and assis tant may be able easily and comfortably to reach the operative field. Any one of the common small instrument tables is satisfactory for the instruments. A good operating lamp of the hammer type pro vides satisfactory illumination. Other needed items—scrub sink, sterilizer, and so forth—will be found in any wellequipped animal operating room.
T h e following solutions and ointments are recommended: ( 1 ) 3-percent atropinesulfate solution. ( 2 ) Sodium-pentobarbital solution (45 mgm. per cc. of 10-per cent alcohol solution). ( 3 ) 4-percent co caine solution. ( 4 ) 20-percent argyrol solution. ( 5 ) Sterile physiologic saline solution. ( 6 ) 2-percent fluorescein solu tion. ( 7 ) 1-percent sodium citrate solu tion. ( 8 ) Adrenalin solution (1:1,000). ( 9 ) Penicillin ophthalmic ointment. ( 1 0 ) 1-percent atropine-sulfate ointment.
T h e following instruments (fig. 1) are necessary: ( 1 ) Castroviejo double-bladed knife, for marking the limits of the win dow in the recipient's eye and the limits of the graft in the donor eye. ( 2 ) Castroviejo's special keratome, 4-mm. wide, for making the initial incision into the an terior chamber in both the recipient and the donor eyes. ( 3 ) Modified de Wecker scissors, for cutting the remainder of the incision in both eyes. ( 4 ) Spatula, for lifting the graft from the donor eye and placing it in the recipient eye, and also
I n selecting rabbits for keratoplasty, it is well to obtain an animal weighing five pounds or more. Smaljer rabbits may be used, but the operation becomes more dif ficult on the smaller eye. T h e rabbits should be obtained sufficiently far in ad vance of the operation so that they may occupy their new quarters for at least 10 days prior to surgery. A small percentage of rabbits will die when removed to the small cages that constitute their quarters in the medical school or hospital. Further, it has been found that new rabbits do not
PREPARATION OF THE RABBIT
970
• R E D E R I C K C. S T A N S B U R Y A N D J O S E P H Α. C. W A D S W O R T H
Fig. 1. (Slarisbury and Wad.sworth). Recommended instruments: (1) Castroviejo doublebladed corneal knife; (2) Castroviejo special keratome; (3) modified de Wecker scissors; (4) spatula; (5) needle holder; (6) Elschnig's fixation forceps; (7) fixation forceps; (8) scissors; (9) clamp; small straight toothless forceps; small, curved, toothless for ceps ; (12) speculum.
mosquito
(10)
do well postoperatively. On the other hand, rabbits that are well acclimated to their lot will usually take the anesthesia and operation uneventfully. Six hours prior to the operation, the rabbit is brought to the animal operating rooms, and atropinization of the desig nated eye is started. A drop of 3-percent atropine-sulfate solution is instilled into this eye each hour for six doses. Sodium pentobarbital, intravenously, is used for the anesthesia. A solution is made of 45 mgm. of sodiurn pentobarbi
(11)
tal per cc. of 10-percent alcohol solution, and 1 cc. of the resulting solution is given for each kilogram of body weight. Three fourths of the estimated dosage is slowly injected intravenously lyi hours before operation, and the remainder of the cal culated amount is given one-half hour be fore operation. This will usually be suf ficient, but sometimes it is necessary to introduce a very small additional amount just before fastening the animal into the clamp. After the second injection of sodium
CORNEAL TRANSPLANTATION IN RABBITS pentobarbital, the rabbit will lie quiet and submit to the trimming of the hair around the operative field. T h e hair is re moved from an area at least one centi meter wide around the eye. In addition, all the long whiskers on that side of his head are cut. At this time, a drop of 4percent cocaine solution is instilled into the conjunctival sac. The rabbit is then placed on the operat ing table and fastened into the special clamp (fig. 2 ) . The head is adjusted to fit snugly into the clamp, and the screw is turned down. T h e animal is further immobilized by lashing the extremities to the table (fig. 3 ) . Twenty-percent argyrol solution is then instilled into the conjunc tival sac, washed out with sterile saline, and another drop of 4-percent cocaine solution is instilled. A small sterile sheet, with a diamond-shaped opening for the
Fig. 2 (Stansbury and Wadsworth). Clamp for immobilization of the rabbit. eye, is then placed over the rabbit and fastened with two towel clamps. SURGICAL PROCEDURE
Separation of the lids is obtained by means of the standard eye speculum. Care must be taken when inserting the specu lum to be sure the nictitating meinbrane of the rabbit is caught behind one arm of the speculum. The eyeball is then fixated with Elschnig's forceps, and the area to be removed is marked out with the double-
971
bladed Castroviejo knife. T h e blades of this knife have previously been treated with 2-percent fluorescein solution, so that the knife cuts and stains the cornea
Fig. 3 (Stansbury and Wadsworth). Immobi lization clamp with the rabbit in position. at the same time. Using a 7-0 doublearmed silk corneal suture with atrau matic needles, the continuous corneal suture of Castroviejo is then inserted, placing all the bites 1 mm. from the fluorescein-stained incision (fig. 4 ) . It is our practice to begin the first bite at the 9-o'clock position and to come out at the lower left-hand corner of the s q u a r e ; to begin the second bite at the upper right-hand corner of the square and to come out at the 12-o'clock posi tion ; to begin the third bite at the 6o'clock position and to come out at the lower right-hand corner; to begin the fourth bite at the upper left-hand corner and to come out at the 9-o'clock position. T h e last bite begins at about the 3-o'clock position and comes out about 3 mm. from the limbus. As each bite is placed, the loop of suture so formed is placed be yond the upper left corner of the square. Each succeeding loop is placed on top of the preceding one. O n e end of the suture is then cut off, and a bite is placed in the middle of the square. T h e two ends of this last suture are then fastened in a mosquito clamp.
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FREDERICK C. S T A N S B U R Y A N D J O S E P H A. C. W A D S W O R T H
A keratome incision is then made in the lower right-hand corner of the square, beveling it in the manner described by Castroviejo and Thomas. Care must be exercised in this maneuver to avoid injur ing the lens. By making this incision in the corner of the square, only one cut is left on that leg of the square to be done with scissors. As soon as the anterior
ner. Finally, the upper end is finished in the same manner. While the assistant con tinuously drops citrate solution over the operative field, a similar graft is excised from the donor eye, using the same pro cedure, except that no Moss suture is used, and the instruments are not tilted when cutting. The graft is then picked up with the
Fig. 4 (Stansbury and Wads worth). Steps in placing the suture in the cornea, with arrangement of the loops. chamber is opened, the assistant begins instilling 1-percent sodium-citrate solu tion into the conjunctival sac (to avoid formation of fibrin). While the square is lifted a slight distance above the lens with the mosquito clamp attached to the Moss suture, the lower blade of the de Wecker scissors, tilted in the same manner as was the keratome, is then passed through the keratome incision and the remainder of the lower leg of the square is completed. The scissors are turned and the left hand side of the square is cut. T h e scissors are then brought down to the lower righthand corner of the window, and the righthand side is completed in the same man-
spatula and gently placed in the window in the recipient's cornea. Any rolling of the edges or corners is corrected with the spatula. Then the suture is tightened, us ing the small straight and the small curved utility forceps. W e begin to tighten with the last suture inserted and work backwards to the first one (fig. 5 ) . W h e n all the sutures are snug, and the graft is in good position, a surgeon's knot is tied at the 3-o'clock position, near the limbus. T h e instillation of the citrate solution is then stopped, and a drop of 3-percent atropine solution is instilled. At this point, we inject a small amount of adrenalin solution (1:1,000) subconjunc-
CORNEAL TRANSPLANTATION IN RABBITS tivally. Three through-and-through lid sutures are then put in position—one in the center of the lids, and one 3 to 4 mm. to each side. Before the last suture is tied, penicillin ophthalmic ointment is injected into the conjunctival sac. W h e n the rabbit is taken back to his quarters, a meshed-wire floor is placed in his cage instead of straw. Every other day, postoperatively, 1-percent atropine
973
DISCUSSION ANESTHESIA
Probably no one factor has given us more concern than the administration of the anesthesia. T h e first system tried was to calculate the amount of pentobarbital to be given and to make a slow intra venous injection of this amount. Many rabbits will go into respiratory failure
Fig. 5 (Stansbury and Wadsworth). Final steps in completion of the suture. ointment and penicillin ophthalmic oint ment are instilled into the conjunctival sac. One week after operation, the ani mal is again given the sodium-pentobarbital anesthesia, and the sutures are re moved. If anterior synechiae are present, they are broken up with adrenalin subconjunctivally, or neosynephrin or atro pine in the conjunctival sac. If infection is present, penicillin is used as long as necessary. It is desirable to keep the rab bit 6 to 8 months postoperatively to de termine whether or not the graft will re main transparent.
within 15 minutes if this is done. Once administered, there is practically nothing the operator can do to lighten the effects of the anesthetic. Nonvolatility is one of the characteristics of the barbiturates that makes for a prolonged and continuous anesthesia. This same nonvolatility pre cludes their excretion through the lungs, and so the concentration depends solely on the dosage. Once too much is given, we have been unable to resuscitate the rab bit. Since this was the case, we tried to weigh the rabbit more carefully and to calculate the dosage more accurately. The
974
FREDERICK C. STANSBURY AND fOSEPH A. C. WADSWORTH
response to pentobarbital is quite variable in dif¥ercnt rabbits, however, as it is in human beings. Large rabbits may die with less than the calculated dosage, and small ones may require double the estimated amount. T h e attempt was made to give the anes thetic intraperitoneally, but here the ab sorption was very slow and irregular. Large amounts are required for deep anesthesia, and the large number of doses and the amount of lime required to watch the animals precluded this method. A weaker solution of sodium pentobarbital was tried, but this was not found to be satisfactory. Finally, fractionalization of the anes thesia was worked out, and this system has proved satisfactory. Three fourths of the estimated dosage is slowly given in an ear vein 1 ^ hours before operation. One hour later, if the rabbit is not too slug gish, the rest of the dose is given. Just before fastening the animal in the clamp, additional pentobarbital is given as needed. This method of fractionalization of the administration of the anesthesia has resulted in no deaths. S K I ' A R A T I O N OK T H E
t.lDS
Wide separation of the eyelids, without the interference of cumbersome instru ments, is necessary during the operation: (1) lo provide an operative field, and ( 2 ) to prevent pressure on the globe. In the rabbit we have tried three methods of holding the lids a p a r t : ( 1 ) the conven tional speculum, (2) sutures through the lids, and ( 3 ) Castroviejo mosquito lidclamps. Advantages of the speculuin are ease and quickness of insertion and eliinination of trautna to the lids. Some workers (Castroviejo, 1941,) believe that it inter feres to some slight degree with instru mentation in the operative area, especially during use of the double-bladed knife,
and that it does not provide as large an exposure as the other two methods. Lid sutures provide a satisfactory op erative field and arc particularly effica cious in immobilizing the nictitating mem brane. However, their disadvantages are considerable. They are painful and often arouse the rabbit. They may cause hema tomas of the lids. They often result in bleeding, and blood in the conjuncti\-aI sac, postoperatively, is undesirable be cause it forms an excellent medium for bacterial growth. Castroviejo's lid clamps also provide a good field and do not have the disadvan tages of the lid sutures. Nevertheless, the small drape used in rabbit surgery does not constitute a good anchor. Lid sutures and lid clamp may produce loo much trac tion and may cause tenting of the lids, which will result in poor exposure. .^fter trying the second and third meth ods on a number of rabbits, the first method—the use of the lid speculum— was adopted as the least traumatic and the most facile procedure. It is comparaliveh' easy to avoid touching the speculum with any of the cutting instruments simply by rotating the globe with the fixation for ceps until the cornea is in the desired posi tion. Katzin (1946) advocated complete immobilization of the globe by radial su tures in the limbus. This type of immobili zation, in our opinion, is un.satisfactory, not only because its use may endanger the eye but also because it may compel the surgeon to work from awkward angles. M A R K I N G T H E CORNEA
Correct marking of the cornea can be a great help in facilitating a successful transplant. If it is incorrectly done, how ever, the remainder of the procedure may be hindered by numerous unnecessary difficulties. T h e blades of the Castroviejo knife must be parallel and set firmly at the desired width (5 mm. for rabbits).
CORNEAL TRANSPLANTATION IN RABBITS If the blades are not parallel, the result ing wide, ragged line will make it difficult to maintain a perfect square when the window is removed with the scissors. T h e knife must be gently placed on the cornea in such a manner as to exert equal pressure on both blades; otherwise un even lines will be made. Pressure should be sufficient to penetrate the epithelium only. If the marking is too deep, the lines tend to gape and the staining becomes diffuse. Care must be taken not to carry the lines too far along the cornea and cause unnecessary damage to the recipi ent epithelium. T h e second marking must be perpendicular to the first, or a square window will not result. It has been our experience, as well as that of other workers (Carpenter and Smyth, 1946), that fluorescein on a rab bit's cornea will stain the entire cornea in a short time. However, we found that, by applying fluorescein to the knife and al lowing it to dry before marking the cor nea, the treated knife made very fine lines, which had less tendency to dififuse. In marking the donor eye, it is advis able to hold the eye gently in order not to stretch the globe; otherwise, the trans plant may be too small for the prepared area. In addition, if the eye is held too firmly, the lens will be pushed forward and its capsule will be ruptured while the transplant is being removed. Although this is not any great mishap, it adds to the difficulty of accurately cutting and re moving the prepared square. PLACING THE SUTURE
It is essential to the success of a kera toplasty that the suture holding the graft in place be located with exact pre cision. T h e suture in the corneal stroma should be approximately 1 mm. from the incision. If it is placed closer than 1 mm., it is difficult to cut the window without severing the suture. If it is placed farther
975
than 1 mm., it will tend to buckle the ap proximated edges of the cornea and the graft when the suture is tightened at the end of the operation. Furthermore, it is very important that the suture be placed so that the arms of the suture, as they crisscross over the graft, cross exactly over each comer, because these are fa vorite locations for bulging. T h a t means that the suture must enter the cornea pre cisely opposite the apex of the right angle that forms each corner of the window. It was for this reason that Thomas gave up square transplants in favor of the circu lar form (Thomas, 1930). T h e cornea puts up considerable re sistance to the passage of the needle through its substantia propria. If the op erator pulls away from the fixation for ceps, the conjunctiva will not withstand the traction exerted in placing the suture but will give way at the limbus. H o w ever, if the fixation forceps are applied in such a manner that the force of the needle pushes toward the forceps, this ac cident will not occur. W h a t to do with the loops of suture while the operation is being finished is another one of the problems encountered. In order to avoid a snarl of the loops at the time when one wants to tie quickly ^ n d close the wound, it was found neces sary to place the loops to one side in a definite pattern. W e now lay all the loops of the suture to the upper left side, in the following manner. T h e first loop, which may be called the 7-to-l loop, using the numbers as they appear on the face of the clock, is placed to the upper left, over the free end of the suture coming out at the 9-o'clock position. The second loop, called the 12-to-6 loop, is placed above the 7-to-l loop. Likewise the third loop, the 5-to-ll loop, is placed above the 12-to-6 loop, and finally the 9-to-3 loop is placed above the other three. T h e free end extends off to the right (fig. 4 ) .
976
FREDERICK C. STANSBURY AND JOSEPH A. C. WADSWORTH
Some operators place the entire suture, tighten the loops ready to tie, and then loosen the loops again, presumably to be sure the loops are located properly. This has been found unnecessary, provided the systematic steps outlined above are fol lowed. W h a t should be done if a leg of the suture is cut during the operation? W e have found that the corneal canals are very easy to relocate and that the needles will pass through the canals without fric tion; so the cut suture is pulled out and a new one inserted. If one goes too deep with the needle and perforates into the anterior chamber, the needle should be removed and a new canal made. This step is necessary to avoid formation of a fis tula. PROBLEM OF FIBRIN
T h e presence of fibrinogen in the nor mal aqueous of the rabbit results in the formation of fibrin as soon as the an terior chamber is opened, and may be a great bother in the completion of a kera toplasty. It has been our experience, as well as that of others (Thomas, 1934), that a solution of sodium citrate in nor mal saline will obviate the formation of fibrin. Just as soon as the anterior chamber is opened, a continuous drip of 1-percent sodium citrate in saline should begin and be continued until the suture has been tightened and tied. If such a system is not maintained, troublesome collections of fibrin will accumulate within the win dow of the cornea and will render the placement of the graft more difficult. The loops of the suture must also be bathed in the citrate, or the firm snarling of the loops will endanger proper placement and lessen the chances for a satisfactory transplant. Not infrequently the coagula tion may be so severe and firm that it is almost impossible to separate the sutures
from one another. T h e removal of the fibrin is so tedious and traumatic that the graft may be poorly placed. Soaking of the suture material in citrate before the sutures are placed in the cornea will help to maintain their pliability and softness. TYING THE SUTURE
T h e mere matter of tightening the loops and tying the suture would appear very simple, but such is not always the case. If the loops are not kept in some pattern so that the operator can identify them, he will find a snarl of silk before him. However, if they are arranged as has been described, the tying can be ex pedited. W e use the two small forceps, one for lifting up the loop and the other for pull ing it through the cornea. First we lift up the 9-to-3 loop and pull it through loosely (fig. 5 ) , pulling on the free end of the suture near the limbus at the 3-o'clock position. Next the 5-to-ll loop is lifted up and pulled through at the 6-o'clock position. Then we lift up the 12-to-6 loop and pull it through at the 1-o'clock posi tion. Finally, the 7-to-l loop is lifted up and pulled through at the 9-o'clock posi tion. T h e apposition of the graft is then checked all around the periphery, using the spatula for any necessary adjust ments. W i t h the same two forceps, this pro cedure is now repeated and all the loops are given a final tightening. T h e y are pulled as tight as can be done without dimpling or buckling the cornea at any place, either on the graft or on the recipi ent's own cornea. This is very important, because the suture controls the apposi tion of the cut surfaces and, if snug enough, prevents bulging. T h e suture is tied near the limbus, first with a surgeon's knot to hold the wet suture material and then with a conventional tie. Finally, the spatula may be inserted between the
CORNEAL TRANSPLANTATION IN RABBITS
977
Fig. 6. (Stansbury and Wadsworth). Pictures of rabbits after transplantation. (1), (2), and (3) show successful results. (4) is a postoperative ectasia. center of the graft and the crossing loops of the suture and gently lifted once or twice, to give a last general distribution of the tension of the suture. L I D CLOSURE
Simple through-and-through fine black silk sutures, placed at equal intervals through the lid margins, give a very sat isfactory closure of the lids. Numerous other methods were tried in an endeavor to obtain pressure, but various disadvan tages precluded their adoption. T w o mat tress sutures were tried, but they were more traumatic and several troublesome postoperative infections resulted. M o r e over, they frequently pulled through,
probably the result of the rabbit's efforts to remove the uncomfortable sutures. In an effort to maintain pressure, a wide overlapping of the lids with mattress su tures was tried, but the resulting irrita tion and secondary infection made this method impracticable. POSTOPERATIVE ECTASIA
O n e of the difficulties we have not been able to overcome is the postoperative bulg ing of the central portion of the cornea, including the graft. Often, when we re move the sutures on the 7th or 8th day, we find the graft in good position, the anterior chamber reformed, no synechiae and no infection, only to be followed a
978
F R E D E R I C K C. S T A N S B U R Y A N D J O S E P H A. C. W A D S W O R T H
day or two later
by very considerable
sutures one week after operation and the
bulging of the whole center of the cornea,
corneal suture about 10 days postopera-
with the graft at the apex of the conus.
tively. W e have not employed this system
Some of these cases have progressed sat-
long enough to determine its efficacy.
isfactorily to complete healing of the scar,
CONCLUSION
and the graft has remained in place and transparent for over six months (fig. 6 ) . W e attribute this type of unsuccessful re_-
A satisfactory method of
keratoplasty
on rabbits, following in general the tech-
sult to our inability to apply a pressure
nique of Castroviejo, is described. A list
bandage to the rabbit's eye. These obser-
of the necessary equipment and a detailed
vations make fibrin fixation of the cornea
description of the procedure followed are
without suture (Katzin, 1946) appear a
recorded. T h e numerous
most unlikely procedure. W e h a v e been
countered, and our methods of
unable to prevent this condition in some
these difficulties are discussed,
rabbits, although we now remove the lid
635 West
165th Street
difficulties
en-
solving
(32).
REFERENCES Bellows, J. G. Influence of local antiseptics on regeneration of corneal epithelium in rabbits. Arch' of Ophth., 1946, v. 36, July, p. 70. Carpenter, C. P., and Smyth, H . F. Chemical burns of the rabbit cornea. Amer. Jour. Ophth., 1946, V. 29, Nov., p. 1363. Castroviejo, R. New Method of corneal transplantation: Final report. Proc. Staff. Meet. Mayo Clinic, 1931, v. 6, Nov. 11, p. 669. . Keratoplasty: An historical and experimental study, including a new method. Amer. Jour. Ophth., 1932, v. 15, Sept., p. 825; Oct., p. 905. . Present status of keratoplasty. Arch, of Ophth., 1939, v. 22, July, p. 114. . Mosquito lid-clamp retractors. Amer. Jour. Ophth., 1939, v. 22, p. 1018. Keratoplasty. Amer. Jour. Ophth., 1941, v. 24, Jan., p. 1; Feb., p. 139. Filatov, \". P. Transplantation of the cornea. Arch, of Ophth,, 1935, v. 13, Mar., p. 321. . Experimental transplantation of the dried and frozen corneas. Vestnik. oftal., 1940, V. 17, p. 536. Transplantation of the cornea, Amer, Rev, Sov, Med,, 1944, v. 2, D e c , ii. 159. Katzin, H. M. Aqueous fibrin fixation of corneal transplants in the rabbit. Arch, of Ophth., • 1946, v. 35, Apr., p. 415. . Animal operating equipment for experimental ocular surgery. Arch, of Ophth,, 1946, v. 36, Aug., p. 215. Sollmann, Τ. A Manual of Pharmacology and Its Api)lication to Therapeutics and Toxicology. Philadelphia, W, B, Saunders Co,, 1937. Thomas, W . T, Transplantation of the cornea: A preliminary report on a series of experi ments in rabbits, together with a demonstration of four rabbits with clear corneal grafts. Trans. Ophth. Soc, United Kingdom, 1930, v, 50, p. 127. . Successful grafting of the cornea in rabbits. Lancet, 1931, v. 1, Feb. 14, p. 335. . Return of sensitivity in grafts in rabbits. Proc. Roy. Soc. Lond., 1931, v. 108, June, l , p . 301. . Transplantation of scleral tissue on to a rabbit's cornea. Trans, Ophth, Soc. United Kingdom, 1932, v, 52, p. 64, . Experimental grafts of devitalized corneal tissue. Trans. Ophth. Soc. United King dom, 1934, V . 54, p. 119. Experimental heterogenous corneal grafts. Trans, Ophth, Soc, United Kingdom, 1936, V. 56, p. 97.